As one of the honorees at Thursday's centenarian celebration in Houston, she announced herself during introductions and began talking about her days as a refund clerk for the City of New York. When she got to her point and someone reached for the microphone, she was firm but hilarious — "I'm not finished yet."

Katz is among the human race's physiological elite - those who have attained triple-digit ages. They've dodged heart disease, the No. 1 killer of Americans, while sidestepping or surviving cancer and accidents.

Some of the healthiest gathered at Clarewood House in southwest Houston, itself home to six centenarians, to celebrate "a century of sunrises."

Organizers had hoped to break an international record, but drew a still-impressive 19 people 100 and older. According to Guinness World Records, the largest gathering involved 28 centenarians last September at a tea party in the United Kingdom.

The oldest of the Houston honorees, 105-year-old Wilminer Carl, is considered a semi-supercentenarian. (Those who live to 110 or longer are called supercentenarians.) Just two were men, which tracks with the reality that women, on average, live longer.

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John Arnold, a master of super-longevity at 102, was general manager for the area's Interstate Theatres - a chain of movie palaces. The native Houstonian lives with a granddaughter and said he stays ticking by just "keeping up with the family."

The United States has an estimated 79,000 centenarians, more than any nation, and that number could swell to more than 600,000 by mid-century.

"The older you live, the healthier you have been," said Dr. Robert N. Butler, president and CEO of the International Longevity Center in New York City. Most centenarians "didn't smoke, they didn't drink excessively, they have personal relationships that are pretty darn good, they have a sense of humor, they care about life and what life offers and they have a sense of purpose," said Butler, 83. "That's the mainstream. There are those who like to shock us, who do all the wrong things and live."

Life expectancy growing

At 78 years, U.S. life expectancy is at an all-time high. Women are living an average 80 years and men can expect to last until 75. Half of the nation's children born in 2000 are projected to live to be at least 101, according to a global aging report published in The Lancet last year.

"Thanks to improvements in nutrition, health and health care, the population aged 100 and over is increasing notably," a report released last year by the U.S. Census Bureau said.

The numbers are growing even faster in developing nations. By 2050, the global centenarian population could reach 2.3 million, according to United Nations estimates, compared to roughly 358,000 today.

Dr. Thomas Perls, a geriatrician at Boston Medical Center and director of the New England Centenarian Study, said longevity is generally about 30 percent genes and 70 percent behavior and health habits.

"When you start going into the late 90s and early 100s, I think there's an increasing genetic component, but exactly how much? We're still a little unclear, but certainly the older and older, the stronger and stronger the genes," he said. "Some of them do have illnesses that have lasted quite a long time, but they cope with those much better than other people. They have the functional reserve to allow them to be better survivors, and they certainly seem to have a tremendous resistance to Alzheimer's disease."

Ten to 15 percent of centenarians live independently, Perls said, while the others require mild to significant assistance. Usually, the need for help is a recent development.

"The price you pay for living 100 years is somewhere around five years disability, which to me is a fantastic thing," Perls said. "We don't need some magic pill. For most of us to be aged, we just need to take on healthy habits."

Staying active

Anna Louise Bruce Robinson, 100, had lived on her own in New Orleans before surviving Hurricane Katrina at age 95. She worked various jobs in her life, played the piano for churches, stayed physically fit and earned a college degree in her 60s.

"They are pretty incredible human beings - bionic, if you will. They believed in physical activity before jogging and all of this stuff was cool," she said. "And, they have an incredible positive attitude. It's so striking."

When his first wife died, Henry Prentice took on raising his four kids - ages 3 to 16 - alone until remarrying nine years later. The mechanical engineer worked in the Ohio ceramics industry and retired in Florida before moving to Houston three years ago.

Now 100, he speaks in a strong voice and still handles his affairs. He even recalled his only driving accident in 85 years on the road with a chuckle.

"I crashed up the car and it didn't smash me," he said. "I'm lucky, I guess."